Feed unit, feed system, and electronic device for increasing power supplied to a battery based on a device state and/or a control of a charging current

ABSTRACT

A feed unit includes: a power transmission section configured to perform power transmission using a magnetic field or an electric field, to a device to be fed including a secondary battery; and a power-transmission control section configured to control power transmission operation in the power transmission section. In a charging period in which charging to the secondary battery is performed based on transmitted power in the power transmission, when the device to be fed including the secondary battery is activated, the power-transmission control section controls the power transmission operation, to increase the transmitted power.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 16/295,466, filed Mar. 7, 2019, which is acontinuation of U.S. application Ser. No. 15/972,669, filed May 7, 2018,now U.S. Pat. No. 10,270,278, which is a continuation of U.S.application Ser. No. 15/428,938, filed Feb. 9, 201, now U.S. Pat. No.9,991,733, which is a continuation of U.S. application Ser. No.14/357,915, filed May 13, 2014, which is now U.S. Pat. No. 9,960,627,the entire contents of each of which is hereby incorporated herein byreference. U.S. application Ser. No. 14/357,915 is a National Stageapplication of International Application No. PCT/JP2012/082009, filedDec. 11, 2012, which claims the benefit of priority from Japanese PatentApplication Nos. 2012-094334, filed Apr. 18, 2012, and 2011-279239,filed Dec. 21, 2011. The benefit of priority is claimed to each of theforegoing.

TECHNICAL FIELD

The present disclosure relates to a feed system that performsnon-contact electric power supply (power transmission, electric powertransmission) to a device to be fed such as an electronic device, aswell as a feed unit and an electronic device applied to such a feedsystem.

BACKGROUND ART

In recent years, attention has been given to a feed system (anon-contact feed system, a wireless charging system) that performsnon-contact electric power supply (power transmission, electric powertransmission) to a CE device (Consumer Electronics Device) such as amobile phone and a mobile music player. This makes it possible to startcharging merely by placing an electronic device (a secondary-sidedevice) on a charging tray (a primary-side device), instead of startingcharging by inserting (connecting) a connector of a power-supply unitsuch as an AC adapter into the device. In other words, terminalconnection between the electronic device and the charging tray becomesunnecessary.

As a method of thus performing non-contact electric power supply, anelectromagnetic induction method is well known. In addition, in recentyears, a non-contact feed system using a method called a magneticresonance method utilizing an electromagnetic resonance phenomenon hasalso been receiving attention. Such non-contact feed systems aredisclosed in, for example, Patent Literatures 1 to 6.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2001-102974

Patent Literature 2: WO 00/27531

Patent Literature 3: Japanese Unexamined Patent Application PublicationNo. 2008-206233

Patent Literature 4: Japanese Unexamined Patent Application PublicationNo. 2002-34169

Patent Literature 5: Japanese Unexamined Patent Application PublicationNo. 2005-110399

Patent Literature 6: Japanese Unexamined Patent Application PublicationNo. 2010-63245

SUMMARY OF THE INVENTION

Incidentally, in a non-contact feed system like those described above,in general, it is expected to improve convenience of a user, byappropriately controlling charging to a battery (a secondary battery) ina device to be fed such as an electronic device.

Accordingly, it is desirable to provide a feed unit, a feed system, andan electronic device that are capable of improving convenience of auser, when performing electric power transmission (power transmission)using a magnetic field or an electric field.

A feed unit according to an embodiment of the present disclosureincludes: a power transmission section configured to perform powertransmission using a magnetic field or an electric field, to a device tobe fed including a secondary battery; and a power-transmission controlsection configured to control power transmission operation in this powertransmission section. In a charging period in which charging to thesecondary battery is performed based on transmitted power in the powertransmission, when the device to be fed including the secondary batteryis activated, the power-transmission control section controls the powertransmission operation, to increase the transmitted power

A first feed system according to an embodiment of the present disclosureincludes: one or a plurality of electronic devices (devices to be fed)including a secondary battery; and the feed unit according to theabove-described embodiment of the present disclosure. The feed unit isconfigured to perform electric power transmission using a magnetic fieldor an electric field, to this electronic device.

In the feed unit and the first feed system according to theabove-described embodiments of the present disclosure, in the chargingperiod in which the charging to the secondary battery in the device tobe fed is performed based on the transmitted power in the powertransmission using the magnetic field or the electric field, when thedevice to be fed including the secondary battery is activated, the powertransmission operation is controlled to increase the transmitted power.Therefore, for example, even if the transmitted power is reduced andsuppressed to be low in the charging period, the device to be fed may beallowed to secure electric power necessary for activation of its own,easily from the transmitted power.

An electronic device according to an embodiment of the presentdisclosure includes: a power receiving section configured to receivetransmitted power in power transmission using a magnetic field or anelectric field, from a feed unit; a secondary battery configured to becharged based on the transmitted power received by this power receivingsection; and a control section configured to perform predeterminedcontrol. In a charging period in which charging to the secondary batteryis performed, when the electronic device is activated, the controlsection notifies the feed unit side of a request for an increase of thetransmitted power.

A second feed system according to an embodiment of the presentdisclosure includes: one or a plurality of the electronic devices(devices to be fed) according to the above-described embodiment; and afeed unit configured to perform power transmission using a magneticfield or an electric field, to this electronic device.

In the electronic device and the second feed system according to theabove-described embodiments of the present disclosure, in the chargingperiod in which the charging to the secondary battery is performed basedon the transmitted power in the power transmission using the magneticfield or the electric field, when the electronic device is activated,the feed unit side is notified of the request for the increase of thetransmitted power. Therefore, for example, even if the transmitted poweris reduced and suppressed to be below in the charging period, the feedunit side is caused to increase the transmitted power, which may allowthe electronic device to secure electric power necessary for activationof its own, easily from the transmitted power.

According to the electronic device and the first feed system accordingto the above-described embodiments of the present disclosure, in thecharging period in which the charging to the secondary battery in thedevice to be fed is performed based on the transmitted power in thepower transmission using the magnetic field or the electric field, thetransmitted power is increased when the device to be fed including thesecondary battery is activated. Therefore, even if the transmitted poweris reduced and suppressed to be low in the charging period, the deviceto be fed may be allowed to secure the electric power necessary for theactivation of its own, easily from the transmitted power. Hence, whenthe electric power transmission is performed using the magnetic field orthe electric field, convenience of a user is allowed to be improved.

According to the electronic device and the second feed system accordingto the above-described embodiments of the present disclosure, in thecharging period in which the charging to the secondary battery isperformed based on the transmitted power in the power transmission usingthe magnetic field or the electric field, the feed unit side is notifiedof the request for the increase of the transmitted power, when theelectronic device is activated. Therefore, even if the transmitted poweris reduced and suppressed to be below in the charging period, theelectronic device is allowed to secure the electric power necessary forthe activation of its own, easily from the transmitted power. Hence,when the electric power transmission is performed using the magneticfield or the electric field, convenience of a user is allowed to beimproved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating an appearance configurationexample of a feed system according to an embodiment of the presentdisclosure.

FIG. 2 is a block diagram illustrating a detailed configuration exampleof the feed system illustrated in FIG. 1.

FIG. 3 is a circuit diagram illustrating a detailed configurationexample of each block illustrated in FIG. 2.

FIG. 4 is a timing waveform diagram illustrating an example of a controlsignal for an alternating-current signal generating circuit.

FIG. 5 is a timing chart illustrating an example of each of a feedingperiod and a communication period.

FIG. 6 is a schematic diagram illustrating a load characteristic exampleof a battery in the feed system illustrated in FIG. 3.

FIG. 7 is a schematic diagram illustrating a load characteristic exampleof a charging circuit in the feed system illustrated in FIG. 3.

FIG. 8 is a timing chart illustrating an operation example in a feedsystem according to each of an example and a comparative example.

FIG. 9 is a flowchart illustrating a control example in an electronicdevice according to the example.

FIG. 10 is a flowchart illustrating a power transmission control examplein a feed unit according to the example.

FIG. 11 is a block diagram illustrating a schematic configurationexample of a feed system according to a modification.

FIG. 12 is a schematic diagram illustrating a propagation mode exampleof an electric field in the feed system illustrated in FIG. 11.

MODES FOR CARRYING OUT THE INVENTION

An embodiment of the present disclosure will be described below indetail with reference to the drawings. It is to be noted that thedescription will be provided in the following order.

1. Embodiment (an example in which transmitted power is increased when adevice to be fed is activated in a charging period)2. Modifications (such as an example of a feed system performingnon-contact electric power transmission by using an electric field)

Embodiment [Overall Configuration of Feed System 4]

FIG. 1 illustrates an appearance configuration example of a feed system(a feed system 4) according to an embodiment of the present disclosure,and FIG. 2 illustrates a block configuration example of this feed system4. The feed system 4 is a system (a non-contact type feed system) thatperforms electric power transmission (power supply, feeding, powertransmission) in a non-contact manner by using a magnetic field (byutilizing magnetic resonance, electromagnetic induction, or the like;likewise hereinafter). This feed system 4 includes a feed unit 1 (aprimary-side device) and one or a plurality of electronic devices (here,two electronic devices 2A and 2B; secondary-side devices) each servingas a device to be fed.

In this feed system 4, electric power transmission from the feed unit 1to the electronic devices 2A and 2B may be performed by placing theelectronic devices 2A and 2B on (or, in proximity to) a feeding surface(a power transmission surface) Si in the feed unit 1, as illustrated inFIG. 1, for example. Here, in consideration of a case in which theelectric power transmission to the electronic devices 2A and 2B isperformed simultaneously or time-divisionally (sequentially), the feedunit 1 is shaped like a mat (a tray) in which the area of the feedingsurface Si is larger than the electronic devices 2A and 2B to be fed andthe like.

(Feed Unit 1)

The feed unit 1 is a unit (a charging tray) that performs the electricpower transmission (power transmission) to the electronic devices 2A and2B by using a magnetic field as described above. This feed unit 1 mayinclude, for example, a power transmission unit 11 that includes a powertransmission section 110, an alternating-current (AC) signal generatingcircuit (a high-frequency power generating circuit) 111, and a controlsection (a power-transmission control section) 112, as illustrated inFIG. 2.

The power transmission section 110 is configured to include a powertransmission coil (a primary-side coil) L1 as well as capacitors(resonance capacitors) C1 p and C1 s, which will be described later, andthe like. The power transmission section 110 performs electric powertransmission (power transmission) using an alternating field to each ofthe electronic devices 2A and 2B (specifically, a power receivingsection 210 to be described later), by utilizing the power transmissioncoil L1 as well as the capacitors C1 p and C1 s (see an arrow P1 in FIG.2). Specifically, the power transmission section 110 has a function ofemitting a magnetic field (a magnetic flux) from the feeding surface Sitowards the electronic devices 2A and 2B. This power transmissionsection 110 also has a function of performing predetermined mutualcommunication operation with the power receiving section 210 to bedescribed later (see an arrow C1 in FIG. 2).

The AC signal generating circuit 111 may be, for example, a circuit thatgenerates a predetermined AC signal Sac (high-frequency electric power)intended to perform power transmission, by using electric power suppliedfrom an external power source 9 (a host power source) of the feed unit1. The AC signal generating circuit 111 as described above may beconfigured using, for example, a switching amplifier to be describedlater. It is to be noted that examples of the external power source 9may include a USB (Universal Serial Bus) 2.0 power source (power supplyability: 500 mA, and power supply voltage: about 5 V) provided in a PC(Personal Computer) etc.

The control section 112 performs various kinds of control operation inthe entire feed unit 1 (the entire feed system 4). Specifically, otherthan controlling the power transmission (power transmission operation)and the communication (communication operation) performed by the powertransmission section 110, the control section 112 may have, for example,a function of controlling optimization of transmitted power andauthenticating the secondary-side device. The control section 112 mayfurther have a function of determining that the secondary-side device ison the primary-side device, and a function of detecting a mixture suchas dissimilar metal. Here, when the above-described power transmissioncontrol is performed, operation of the AC signal generating circuit 111is controlled using a predetermined control signal CTL to be describedlater. In addition, this control section 112 also has a function ofperforming modulation processing based on pulse width modulation (PWM)to be described later, by using the control signal CTL.

Further, the control section 112 has a function of performing a stepwisereduction of the transmitted power to a minimum power value necessary incharging, in a period in which each of the electronic devices 2A and 2Bis not being activated, during a charging period in which a battery 214to be described later in each of the electronic devices 2A and 2B ischarged based on the transmitted power using a magnetic field. Inaddition, in such a charging period, the power transmission operation ofthe power transmission section 110 is controlled to increase thetransmitted power, when the electronic devices 2A and 2B are activated.It is to be noted that, by utilizing communication to be described laterwith the electronic devices 2A and 2B, the control section 112 detectswhether each of the electronic devices 2A and 2B is in theabove-described charging period for the battery 214, and whether each ofthe electronic devices 2A and 2B is being activated. Such powertransmission control (feeding control) by the control section 112 willbe described in detail later (FIGS. 8 and 10).

(Electronic Devices 2A and 2B)

The electronic devices 2A and 2B each may be, for example, any ofstationary electronic devices represented by television receivers,mobile electronic devices containing a rechargeable battery (a battery)represented by mobile phones and digital cameras, and the like. Asillustrated in, for example, FIG. 2, the electronic devices 2A and 2Bmay each include a power receiving unit 21, and a load 22 that performspredetermined operation (operation that allows functions of serving asthe electronic device to be performed) based on electric power suppliedfrom this power receiving unit 21. Further, the power receiving unit 21includes the power receiving section 210, a rectifier circuit 211, avoltage stabilizer 212, a charging circuit 213 (a charging section), abattery 214 (a secondary battery), a voltage detecting circuit 215, anda control section 216.

The power receiving section 210 is configured to include a powerreceiving coil (a secondary-side coil) L2 and capacitors C2 p and C2 s(resonance capacitors), which will be described later, and the like. Thepower receiving section 210 has a function of receiving electric power(transmitted power) transmitted from the power transmission section 110in the feed unit 1, by utilizing the power receiving coil L2 as well asthe resonance capacitors C2 p and C2 s, and the like. This powerreceiving section 210 also has a function of performing theabove-described predetermined mutual communication operation with thepower transmission section 110 (see the arrow C1 in FIG. 2).

The rectifier circuit 211 is a circuit that rectifies the transmittedpower (AC power) supplied from the power receiving section 210, andgenerates DC power.

The voltage stabilizer 212 is a circuit that performs predeterminedvoltage stabilization operation, based on the DC power supplied from therectifier circuit 211. Specifically, an input voltage (an input voltageV1 to be described later) obtained based on the transmitted power isstabilized, and an output voltage after the stabilization is supplied tothe charging circuit 213.

The charging circuit 213 is a circuit used to perform charging to thebattery 214, based on the DC power (the above-described output voltage)supplied from the voltage stabilizer 212 after the voltagestabilization.

The battery 214 stores electric power according to the charging by thecharging circuit 213, and may be configured using, for example, arechargeable battery (a secondary battery) such as a lithium ionbattery.

The voltage detecting circuit 215 is a circuit that detects the DCvoltage (the input voltage V1 to the voltage stabilizer 212) outputtedfrom the rectifier circuit 215, and outputs a result of the detection tothe control section 216. Such a voltage detecting circuit 215 may beconfigured using, for example, a resistor and the like.

The control section 216 performs various kinds of control operation ineach of the entire electronic devices 2A and 2B (the entire feed system4). Specifically, for example, the control section 216 may have afunction of controlling the power receiving operation and thecommunication operation by the power receiving section 110, and alsohave a function of controlling operation of each of the voltagestabilizer 212, the charging circuit 213, and the like. It is to benoted that the functions of this control section 216 will be describedin detail later.

[Detailed Configuration of Feed Unit 1 as well as Electronic devices 2Aand 2B]

FIG. 3 illustrates a detailed configuration example of each block in thefeed unit 1 as well as the electronic devices 2A and 2B illustrated inFIG. 2, in a circuit diagram.

(Power Transmission Section 110)

The power transmission section 110 includes the power transmission coilL1 provided to perform electric power transmission using a magneticfield (to generate a magnetic flux), and the capacitors C1 p and C1 sthat form, together with this power transmission coil L1, an LCresonance circuit. The capacitor C1 s is electrically connected to thepower transmission coil L1 in series. In other words, one end of thecapacitor C1 s and one end of the power transmission coil L1 areconnected to each other. Further, the other end of the capacitor C1 sand the other end of the power transmission coil L1 are connected to thecapacitor C1 p in parallel. A connection end between the powertransmission coil L1 and the capacitor C1 p is grounded.

The LC resonance circuit configured of the power transmission coil L1 aswell as the capacitors C1 p and C1 s, and an LC resonance circuit thatwill be described later and configured of the power receiving coil L2 aswell as the capacitors C2 s and C2 p, are magnetically coupled to eachother. As a result, LC resonance operation is performed based on aresonance frequency that is substantially the same as the high-frequencyelectric power (the AC signal Sac) generated by the AC signal generatingcircuit 111 to be described below.

(AC Signal Generating Circuit 111)

The AC signal generating circuit 111 is configured using a switchingamplifier (a so-called class E amplifier) including one transistor (notillustrated) serving as a switching element. The control signal CTL forpower transmission is supplied from the control section 112 to the ACsignal generating circuit 111. This control signal CTL is a pulse signalhaving a predetermined duty ratio, as illustrated in FIG. 3. Further,for example, as illustrated in Parts (A) and (B) of FIG. 4, the pulsewidth modulation to be described later may be performed, by controllingthis duty ratio in the control signal CTL.

In the AC signal generating circuit 11, with such a configuration, theabove-described transistor performs ON/OFF operation (switchingoperation based on a predetermined frequency and duty ratio), accordingto the control signal CTL for power transmission. In other words, theON/OFF operation of the transistor serving as the switching element iscontrolled using the control signal CTL supplied from the controlsection 112. As a result, for example, the AC signal Sac (AC power) maybe generated based on a DC signal Sdc inputted from the external powersource 9 side, and the generated AC signal Sac may be supplied to thepower transmission section 110.

(Power Receiving Section 210)

The power receiving section 210 includes the power receiving coil L2provided to receive electric power (from a magnetic flux) transmittedfrom the power transmission section 110, and also includes thecapacitors C2 p and C2 s that form, together with this power receivingcoil L2, the LC resonance circuit. The capacitor C2 p is electricallyconnected to the power receiving coil L2 in parallel, and the capacitorC2 s is electrically connected to the power receiving coil L2 in series.In other words, one end of the capacitor C2 s is connected to one end ofthe capacitor C2 p and one end of the power receiving coil L2. Further,the other end of the capacitor C2 s is connected to one input terminalin the rectifier circuit 211, and the other end of the power receivingcoil L2 as well as the other end of the capacitor C2 p are connected tothe other input terminal in the rectifier circuit 211.

The LC resonance circuit configured of the power receiving coil L2 aswell as the capacitors C2 p and C2 s, and the above-described LCresonance circuit configured of the power transmission coil L1 as wellas the capacitors C1 p and C1 s are magnetically coupled to each other.As a result, the LC resonance operation is performed based on aresonance frequency that is substantially the same as the high-frequencyelectric power (the AC signal Sac) generated by the AC signal generatingcircuit 111.

(Rectifier Circuit 211)

Here, the rectifier circuit 211 is configured using four rectifierelements (diodes) D1 to D4. Specifically, an anode of the rectifierelement D1 and a cathode of the rectifier element D3 are connected tothe one input terminal in the rectifier circuit 211, and a cathode ofthe rectifier element D1 and a cathode of the rectifier element D2 areconnected to an output terminal in the rectifier circuit 211. Further,an anode of the rectifier element D2 and a cathode of the rectifierelement D4 are connected to the other input terminal in the rectifiercircuit 211, and an anode of the rectifier element D3 and an anode ofthe rectifier element D4 are grounded. In the rectifier circuit 211,with such a configuration, the AC power supplied from the powerreceiving section 210 is rectified, and received electric power that isthe DC power is supplied to the voltage stabilizer 212.

(Voltage Stabilizer 212)

The voltage stabilizer 212 is, as described above, a circuit thatstabilizes the DC power (the input voltage V1) supplied from therectifier circuit 211, and may be configured using, for example, a powercircuit such as a switching regulator.

(Charging Circuit 213)

The charging circuit 213 is, as described above, a circuit that performscharging to the battery 214 based on the output voltage (the DC power)from the voltage stabilizer 212. Here, the charging circuit 213 isdisposed between the voltage stabilizer 212 and the load 22.

(Voltage Detecting Circuit 215)

The voltage detecting circuit 215 is, as described above, a circuit thatdetects the input voltage V1 to the voltage stabilizer 212, and therebydetects to what extent unnecessary electric power (electric power thatexceeds the minimum power value necessary in charging to the battery214) to be described later has been received.

(Control Section 216)

The control section 216 performs various kinds of control operation ineach of the entire electronic devices 2A and 2B (the entire feed system4) as described above, and also has the following functions in thepresent embodiment in particular. Specifically, there is provided afunction of first obtaining and grasping various pieces of deviceinformation in the device (the electronic device 2A or the electronicdevice 2B) of its own whenever necessary. Specifically, information(activation status information) indicating an activation status of thedevice (the load 22) of its own (itself) is obtained from the load 22.Further, information (input voltage information) indicating a magnitudeof the above-described input voltage V1 is obtained from the voltagedetecting circuit 215. Information (power-remaining-amount information:for example, a battery voltage Vb illustrated in FIG. 3) indicating apower remaining amount in the battery 214 is also obtained from thecharging circuit 213.

The control section 216 has functions such as a function of notifyingthe feed unit 1 side (the control section 112) of a request for anincrease of the transmitted power, upon determining that the device ofits own is activated in the charging period for the battery 214, byutilizing these obtained pieces of device information. It is to be notedthat such notifying the feed unit 1 side is performed utilizingcommunication using the power receiving section 210. Such control(power-transmission request control) by the control section 216 will bedescribed in detail later (FIGS. 8 and 9).

[Functions and Effects of Feed System 4]

1. Summary of Overall Operation

In this feed system 4, based on the electric power supplied from theexternal power source 9, the predetermined high-frequency electric power(the AC signal Sac) used to perform the electric power transmission issupplied from the high-frequency power generating circuit 111 in thefeed unit 1, to the power transmission coil L1 as well as the capacitorsC1 p and C1 s (the LC resonance circuit) in the power transmissionsection 110. This causes the magnetic field (the magnetic flux) in thepower transmission coil L1 in the power transmission section 110. Atthis moment, when the electronic devices 2A and 2B each serving as adevice to be fed (a device to be charged) are placed on (or, inproximity to) the top surface (the feeding surface Si) of the feed unit1, the power transmission coil L1 in the feed unit 1 and the powerreceiving coil L2 in each of the electronic devices 2A and 2B are inproximity to each other in the vicinity of the feeding surface Si.

In this way, when the power receiving coil L2 is placed in proximity tothe power transmission coil L1 generating the magnetic field (themagnetic flux), an electromotive force is generated in the powerreceiving coil L2 by being induced by the magnetic flux generated by thepower transmission coil L1. In other words, due to electromagneticinduction or magnetic resonance, the magnetic field is generated byforming interlinkage with each of the power transmission coil L1 and thepower receiving coil L2. As a result, electric power transmission fromthe power transmission coil L1 side (a primary side, the feed unit 1side, or the power transmission section 110 side) to the power receivingcoil L2 side (a secondary side, the electronic devices 2A and 2B side,or the power receiving section 210 side) is performed (see the arrow P1in FIGS. 2 and 3). At this moment, the power transmission coil L1 on thefeed unit 1 side and the power receiving coil L2 on the electronicdevices 2A and 2B side are magnetically coupled to each other by theelectromagnetic induction or the like, so that the LC resonanceoperation is performed in the above-described LC resonance circuits.

Then, in each of the electronic devices 2A and 2B, the AC power receivedby the power receiving coil L2 is supplied to the rectifier circuit 211,the voltage stabilizer 212, and the charging circuit 213, and thefollowing charging operation is performed. Specifically, after this ACpower is converted into predetermined DC power by the rectifier circuit211, and the voltage stabilization operation is performed by the voltagestabilizer 212, the charging to the battery 214 based on this DC poweris performed by the charging circuit 213. In this way, in each of theelectronic devices 2A and 2B, the charging operation based on theelectric power received by the power receiving section 210 is performed.

In other words, in the present embodiment, at the time of charging theelectronic devices 2A and 2B, terminal connection to an AC adapter orthe like, for example, may be unnecessary, and it is possible to startthe charging easily by merely placing the electronic devices 2A and 2Bon (or in proximity to) the feeding surface Si of the feed unit 1(non-contact feeding is performed). This reduces burden on a user.

Further, as illustrated in, for example, FIG. 5, at the time of suchfeeding operation, a feeding period Tp (a charging period for thebattery 214) and a communication period Tc (a non-charging period) aretime-divisionally periodic (or aperiodic). In other words, the controlsection 112 and the control section 216 perform the control so that thefeeding period Tp and the communication period Tc are set to betime-divisionally periodic (or aperiodic). Here, this communicationperiod Tc is a period in which the predetermined mutual communicationoperation (communication operation for authentication between devices,feeding efficiency control, and the like) using the power transmissioncoil L1 and the power receiving coil L2 is performed between theprimary-side device (the feed unit 1) and the secondary-side device (theelectronic devices 2A and 2B) (see the arrow C1 in FIGS. 2 and 3). It isto be noted that a time ratio between the feeding period Tp and thecommunication period Tc at this moment may be, for example, about 9:1.

Here, in this communication period Tc, the communication operation usingthe pulse width modulation in the AC signal generating circuit 111 maybe performed, for example. Specifically, the duty ratio of the controlsignal CTL in the communication period Tc is set based on predeterminedmodulation data, so that the communication based on the pulse widthmodulation is performed. It is to be noted that, it is theoreticallydifficult to perform frequency modulation at the time of resonanceoperation in the power transmission section 110 and the power receivingsection 210 described above. Therefore, such pulse width modulation isused to achieve communication operation easily.

2. About Transmitted Power in Charging Period

Further, in the feed system 4 of the present embodiment, in the periodin which the charging to the battery 214 in each of the electronicdevices 2A and 2B is performed (in the charging period, or a periodbefore completion of charging) based on the transmitted power in thepower transmission using the magnetic field in the manner describedabove, the transmitted power is reduced and suppressed to be low. Inother words, in such a charging period, the control section 112 in thefeed unit 1 controls the power transmission operation performed by thepower transmission section 110, so that the transmitted power is reducedand suppressed to be low. One reason for this is as follows.

Specifically, at first, for example, as illustrated in FIGS. 6 and 7,when the battery 214 is configured of a secondary battery such as alithium ion battery, charging to the secondary battery may be performedusually based on so-called “CC-CV charging”. In other words, chargingcontrol is performed so that a constant-voltage charging (CV charging)period Tcv is set to follow a constant-current charging (CC charge)period Tcc. At the time of such CC-CV charging, a load characteristic (arelationship between charging time and a magnitude of a load) of thebattery 214 may be, for example, as illustrated in FIG. 6, and a loadcharacteristic of the charging circuit 213 may be, for example, asillustrated in FIG. 7. In other words, as indicated by an arrow of abroken line in each of FIGS. 6 and 7, as the charging to the battery 214proceeds, a gap occurs between the transmitted power and the electricpower necessary in charging, and an amount corresponding to the gapbecomes “surplus power ((excessive (unnecessary) transmitted power)” ifthe gap is left as it is. Such surplus power eventually becomes “heat”,which heats the feed unit 1 as well as the electronic devices 2A and 2B,and therefore is a problem.

For this reason, in the present embodiment, in the period in which eachof the electronic devices 2A and 2B is not activated during the chargingperiod for the battery 214, the control section 112 performs control fora stepwise reduction of the transmitted power to the minimum power valuenecessary in charging. Further, the control section 216 in each of theelectronic devices 2A and 2B side notifies the feed unit 1 (the controlsection 112) side of a request for a stepwise reduction of thetransmitted power to the minimum power value necessary in charging, inthe period in which the device of its own is not activated during thecharging period.

FIG. 8 illustrates an operation example in the charging period, in atiming chart, in which Part (A) illustrates the magnitude of the load22, Part (B) illustrates transmitted power in a feed system according toa comparative example, and Part (C) illustrates transmitted poweraccording to an example of the present embodiment.

In this operation example, as indicated by an arrow P21 in this figure,the control section 112 reduces the transmitted power stepwise, bydecreasing (or increasing) the transmitted power one step at a time, inresponse to a request from each of the electronic devices 2A and 2B (thecontrol section 216). One reason for this is as follows. Specifically,first, for example, when the load 22 is lightened as indicated by anarrow P22 in this figure, a voltage such as the above-described inputvoltage V1 to the voltage stabilizer 212 may rise. Therefore, a minimumvoltage value (a threshold voltage Vth1 to be described later; amagnitude of the input voltage V1, which ensures operation of thevoltage stabilizer 212 (for example, the switching regulator)) in thisinput voltage V1 is defined, and the transmitted power is graduallyreduced (one step at a time) to the extent not to fall below thisminimum voltage value.

Specifically, as will be described in detail later, when the transmittedpower is larger than the minimum power value necessary in charging(corresponding to the above-described threshold voltage Vth1), thecontrol section 216 notifies a request for a decrease of the transmittedpower by one step. On the other hand, when the transmitted power issmaller than the minimum power value (the threshold voltage Vth1), thecontrol section 216 notifies a request for an increase of thetransmitted power by one step. Subsequently, in response to such arequest for the increase or decrease of the transmitted power, thecontrol section 112 actually increases or decreases the transmittedpower, one step a time. Such control of the transmitted power preventsuseless (unnecessary) power transmission (charging) to the electronicdevices 2A and 2B, and avoids heat and the like due to theabove-described surplus transmitted power. It is to be noted that theabove-described “minimum power value necessary in charging” may bepreferably defined by not only the magnitude of the input voltage V1 inthe voltage stabilizer 212, but also a magnitude of the output voltagefrom this voltage stabilizer 212. This is to allow more reliabledetermination as to whether functions of the voltage stabilizer 212 arenot stopped as will be described later.

2-1. Comparative Example

However, in a case in which the transmitted power is thus reduced whilea light state of the load 22 continues, the following issue arises in acomparative example, when each of the electronic devices 2A and 2B (theload 22) is activated as indicated by an arrow P31 in this figure (suchas automatic activation by a timer or the like, and manual activation bya user).

Specifically, first, the transmitted power at that time may besignificantly below maximum power necessary for the load 22. At the timeof such an overload, although electric power is necessary for thecharging circuit 213, the voltage stabilizer 212 (for example, theswitching regulator) with the reduced transmitted power is not allowedto supply the charging circuit 213 with the electric power. Therefore,the charging circuit 213 supplies the load 22 with electric power, byutilizing a part of the charging power accumulated in the battery 214.In such a state, the input voltage V1 to the voltage stabilizer 212suddenly drops, and the voltage stabilizer 212 enters a so-called UVLO(Under Voltage Lock Out) mode. In other words, the voltage stabilizer212 configured of the switching regulator or the like stops thefunctions thereof, and does not supply the electric power to thecharging circuit 213.

In such a UVLO mode, the load 22 being activated is supplied with thepart of the charging power from the charging circuit 213 as describedabove, and therefore operates smoothly. On the other hand, the voltagestabilizer 212 in the UVLO mode is an electrically very light load. As aresult, in an activated period (an activated-state period Ton) of theload 22, as indicated by an arrow P103 in the figure, the transmittedpower is steadily reduced, because the voltage stabilizer 212 is a verylight load even though the load 22 is in a heavy state.

In this way, in the comparative example illustrated in Part (B) of FIG.8, although it is necessary to increase the transmitted power and thereis sufficient transfer capability, the transmitted power is steadilyreduced, and as a result, the amount of remaining power in the battery214 continuously decreases, which impairs convenience of a user.

2-2. Present Embodiment

Therefore, in the feed system 4 of the present embodiment, when each ofthe electronic devices 2A and 2B is activated in the charging period forthe battery 214, the control section 112 in the feed unit 1 controls thepower transmission operation of the power transmission section 110 toincrease the transmitted power (see an arrow P32 in Part (C) of FIG. 8).Further, the control section 216 in each of the electronic devices 2Aand 2B side notifies the feed unit 1 side (the control section 112) of arequest for an increase of the transmitted power, upon determining thatthe device (the load 22) of its own is activated in such a chargingperiod.

At this moment, by utilizing the communication with the electronicdevices 2A and 2B, the control section 112 detects whether each of theelectronic devices 2A and 2B is in the charging period for the battery214, and whether each of the electronic devices 2A and 2B (the load 22)is being activated. Further, the control section 216 notifies the feedunit 1 (the control section 112) side, by utilizing the communicationwith the feed unit 1. In the present embodiment, such control of thetransmitted power results in the following, unlike the comparativeexample. Specifically, as described above, even if the transmitted poweris reduced and suppressed to be low in the charging period, each of theelectronic devices 2A and 2B readily secures electric power necessaryfor activation of its own, from the transmitted power.

It is to be noted that, in this process, as indicated by an arrow P33and a diagonally shaded portion in Part (C) of FIG. 8, the controlsection 216 performs control so that activation operation of the load 22is performed using a part of the charging power accumulated in thebattery 214, in a period before the transmitted power actually increasesin response to the request for the increase of the transmitted power.This is because this period corresponds to a time lag in thecommunication from the electronic devices 2A and 2B side to the feedunit 1 side, and in this period, it is necessary to perform theactivation operation by receiving support from the charging power.

(Control Example in Electronic Devices 2A and 2B)

Here, FIG. 9 illustrates a specific control example of the controlsection 216 in each of the electronic devices 2A and 2B (a controlexample in the charging period), in a flowchart. In this controlexample, first, normal power receiving operation (operation of receiving100% of the transmitted power) is performed in the power receivingsection 210 (step S101).

Next, the control section 216 resets (initializes) a predetermined powerreceiving counter (Count=0: step S102). Subsequently, the controlsection 216 determines, by using the power-remaining-amount informationserving as the above-described device information, whether a powerremaining amount in the battery 214 is equal to or larger than apredetermined threshold, i.e., whether charging to the battery 214 iscompleted (step S103). Specifically, here, whether the battery voltageVb is equal to or larger than a predetermined threshold voltage Vth isdetermined.

Here, upon determining that the battery voltage Vb is equal to or largerthan the threshold voltage Vth (step S103: Y), the control section 216determines that the charging to the battery 214 is completed, andnotifies this result (transmits a charging completion command) to thefeed unit 1 (the control section 112) side (step S104). This ends thecontrol by the control section 216 in the charging period illustrated inFIG. 9. It is to be noted that this notification (the chargingcompletion command) is performed utilizing the communication with thefeed unit 1.

On the other hand, upon determining that the battery voltage Vb issmaller than the threshold voltage Vth (step S103: N), the controlsection 216 determines that the charging to the battery 214 is not yetcompleted), and increases the value of the power receiving counter byone (Count=Count+1: step S105). The control section 216 then determineswhether this value of the power receiving counter is equal to or largerthan a predetermined threshold Th (whether Count≥Th is satisfied) (stepS106).

Here, when it is determined that the value of the power receivingcounter is smaller than the threshold Th (Count<Th) (step S106: N), theflow returns to step S103 described above. On the other hand, upondetermining that the value of the power receiving counter is equal to orlarger than the threshold Th (Count≥Th) (step S106: Y), the controlsection 216 then determines, by using the above-described activationstatus information serving as the device information, whether the device(the load 22) of its own is being activated (step S107).

Here, upon determining that the load 22 is being activated (step S107:Y), the control section 216 notifies a request for an increase of thetransmitted power (transmits a necessary-transmitted-power requestingcommand) to the feed unit 1 side (the control section 112) as describedabove (step S108). In other words, the control section 216 notifies thefeed unit 1 side of a request, to bring the transmitted power to thepower value necessary in activation. This notification (thenecessary-transmitted-power requesting command) is also performedutilizing the communication with the feed unit 1. It is to be noted thatthe flow subsequently returns to step S102 described above.

On the other hand, upon determining that the load 22 is not beingactivated (step S107: N), the control section 216 then determineswhether the input voltage V1 to the voltage stabilizer 212 is largerthan or smaller than the threshold voltage Vth1 corresponding to theminimum power value necessary in charging (step S109). It is to be notedthat, as described above, this threshold voltage Vth1 corresponds to themagnitude of the input voltage V1, the magnitude ensuring the operationof the voltage stabilizer 212 (for example, the switching regulator).

Here, when the input voltage V1 is larger than the threshold voltageVth1 (V1>Vth1, step S109: Y), the control section 216 determines thatthe transmitted power is larger than the minimum power value necessaryin charging, and notifies the feed unit 1 (the control section 112) sideof a request for a decrease of the transmitted power by one step. Inother words, the control section 216 transmits anecessary-transmitted-power one-step-down requesting command to the feedunit 1 side (step S110). This notification (thenecessary-transmitted-power one-step-down requesting command) is alsoperformed utilizing the communication with the feed unit 1. It is to benoted that the flow subsequently returns to step S102 described above.

On the other hand, when the input voltage V1 is smaller than thethreshold voltage Vth1 (V1<Vth1, step S109: N), the control section 216determines that the transmitted power is smaller than the minimum powervalue necessary in charging, and notifies the feed unit 1 (the controlsection 112) side of a request for an increase of the transmitted powerby one step. In other words, the control section 216 transmits anecessary-transmitted-power one-step-up requesting command to the feedunit 1 side (step S111). This notification (thenecessary-transmitted-power one-step-up requesting command) is alsoperformed utilizing the communication with the feed unit 1. It is to benoted that the flow subsequently returns to step S102 described above.

In this way, in the charging period in which the charging to the battery214 is performed based on the transmitted power, the request for anincrease of the transmitted power is notified from each of theelectronic devices 2A and 2B to the feed unit 1 side, when the deviceitself (the electronic device 2A or the electronic device 2B) isactivated. This causes the feed unit 1 side to increase the transmittedpower even if the transmitted power is reduced and suppressed to bebelow in the charging period as described above. Therefore, in each ofthe electronic devices 2A and 2B, this makes it easy to secure theelectric power necessary for the activation of its own, from thetransmitted power.

(Power Transmission Control Example in Feed Unit 1)

On the other hand, FIG. 10 illustrates a specific power transmissioncontrol example (a power transmission control example in the chargingperiod) of the control section 112 in the feed unit 1, in a flowchart.In this power transmission control example, first, normal powertransmission operation (operation of transmitting 100% of thetransmitted power) is performed in the power transmission section 110(step S201).

Next, the control section 112 determines whether a predetermined commandfrom each of the electronic devices 2A and 2B (the control section 216)side is received (whether notification is provided for a predeterminedrequest) (step S202). Here, when it is determined that the command isnot received (step S202: N), step S202 is repeated.

On the other hand, upon determining that the command is received (stepS202: Y), the control section 112 then recognizes contents of thecommand by decoding the contents (step S203). Subsequently, the controlsection 112 determines whether charging to the battery 214 is completed(whether the above-described charging completion command is received)(step S204).

Here, upon determining that the charging is completed (step S204: Y),the control section 112 then performs the power transmission control, tostop the power transmission operation by the power transmission section110 (step S205). This prevents useless (unnecessary) power transmission(charging) to the electronic devices 2A and 2B, thereby avoiding heatand the like due to surplus transmitted power. The power transmissioncontrol by the control section 112 in the charging period illustrated inFIG. 10 is then completed.

On the other hand, upon determining that the charging is not yetcompleted (step S204: N), the control section 112 then determines, basedon the contents (the above-described start status information) of thecommand, whether the electronic device (the load 22 in the electronicdevice 2A or the electronic device 2B) is being activated (step S206).

Here, upon determining that the electronic device (the load 22) is beingactivated (step S206: Y), the control section 112 then controls thetransmitted power to bring the transmitted power to a power valuenecessary in activation, requested by the device side (requested in thenecessary-transmitted-power requesting command described above). As aresult, power transmission based on such a necessary power value isperformed by the power transmission section 110 (step S207). It is to benoted that the flow subsequently returns to step S202 described above.

On the other hand, upon determining that the electronic device (the load22) is not being activated (step S206: N), the control section 112 thendetermines, based on the contents of the command, whether atransmitted-power one-step-down request is provided (step S208). Inother words, it is determined whether the necessary-transmitted-powerone-step-down requesting command described above is received, or whetherthe necessary-transmitted-power one-step-up requesting command describedabove is received.

Here, upon determining that the transmitted-power one-step-down requestis provided (the necessary-transmitted-power one-step-down requestingcommand is received) (step S208: Y), the control section 112 thencontrols the transmitted power to decrease the transmitted power by onestep. As a result, power transmission based on the transmitted powerdecreased by one step is performed by the power transmission section 110(step S209). It is to be noted that the flow subsequently returns tostep S202 described above.

On the other hand, upon determining that the transmitted-powerone-step-down request is not provided (the necessary-transmitted-powerone-step-up requesting command is received) (step S208: N), the controlsection 112 controls the transmitted power to increase the transmittedpower by one step. As a result, power transmission based on thetransmitted power increased by one step is performed by the powertransmission section 110 (step S210). It is to be noted that the flowsubsequently returns to step S202 described above.

In this way, when the electronic device (the electronic device 2A or theelectronic device 2B) having the battery 214 is activated in thecharging period in which the charging to the battery 214 is performedbased on the transmitted power, the power transmission operation iscontrolled to increase the transmitted power. This makes it easy in eachof the electronic devices 2A and 2B to secure the electric powernecessary for activation of its own from the transmitted power, even ifthe transmitted power is reduced and suppressed to be low in thecharging period as described above.

As described above, in the present embodiment, when the electronicdevice (the electronic device 2A or the electronic device 2B) having thebattery 214 is activated in the charging period in which the charging tothe battery 214 is performed based on the transmitted power, the controlsection 112 controls the power transmission operation to increase thetransmitted power. Further, the control section 216 notifies the feedunit 1 side of the request for the increase of the transmitted power,when the device (the electronic device 2A or the electronic device 2B)of its own is activated in such a charging period. This causes the feedunit 1 side to increase the transmitted power, even if the transmittedpower is reduced and suppressed to be below in the charging period.Therefore, this makes it easy in each of the electronic devices 2A and2B, to secure the electric power necessary for activation of its ownfrom the transmitted power. Hence, it is possible to improve convenienceof a user, when the electric power transmission using a magnetic fieldis performed.

It is to be noted that the transmitted power (including a combinationwith the charging power in the battery 214) exceeding maximum electricpower necessary in activation of the load 22 is a condition for thecontrol by each of the control sections 112 and 216 in the presentembodiment. Therefore, when such an electric power balance is notsatisfied, part of the functions in the load 22 may be preferablylimited (invalidated) at the time of activating the load 22, and thelike, according to the amount of remaining power in the battery 214.This is because, without such a limit (invalidation), the charging powerin the battery 214 gradually decreases.

Modifications

Technology of the present disclosure has been described above withreference to the embodiment, but the present technology is not limitedto this embodiment and may be variously modified.

For example, the description has been provided using various coils (thepower transmission coil, and the power receiving coil) in theabove-described embodiment, but various kinds of configurations may beused as the configurations (the shapes) of these coils. In other words,each coil may have, for example, a shape such as a spiral shape, a loopshape, a bar shape using a magnetic substance, an a-winding shape inwhich a spiral coil is folded to be in two layers, a spiral shape havingmore multiple layers, a helical shape in which a winding is wound in athickness direction, etc. In addition, each coil may be not only awinding coil configured using a wire rod having conductivity, but also apattern coil having conductivity and configured using, for example, aprinted circuit board, a flexible printed circuit board, etc.

Further, in the above-described embodiment, an electronic device hasbeen described as an example of the device to be fed, but the device tobe fed is not limited thereto and may be any type of device to be fedother than electronic devices (for example a vehicle such as an electriccar).

Furthermore, in the above-described embodiment, each component of thefeed unit and the electronic device has been specifically described.However, it is not necessary to provide all the components, or othercomponent may be further provided. For example, a communicationfunction, a function of performing some kind of control, a displayfunction, a function of authenticating a secondary-side device, afunction of detecting a mixture such as dissimilar metal, and/or thelike may be provided in the feed unit and/or the electronic device.Moreover, the power transmission control (the control of increasing thetransmitted power, when the electronic device that is the device to befed is activated in the charging period) in the above-describedembodiment may be performed only under a predetermined condition,without being uniformly executed at the time of activating theelectronic device. For example, in a case in which a predeterminedsequence (operation) defined beforehand is performed, execution of theabove-described power transmission control may be disabled, even whenthe electronic device is activated. In other words, the above-describedpower transmission control may be executed, for example, when theelectronic device is activated in anything other than theabove-described predetermined sequence, such as when a user activatesthe electronic device by pushing a power button of the electronicdevice.

In addition, the embodiment has been described above by taking mainlythe case in which the plurality of (two or more) electronic devices areprovided in the feed system, as an example. However, without beinglimited to this case, only one electronic device may be provided in thefeed system.

Moreover, the embodiment has been described above by taking the chargingtray for the small electronic device (the CE device) such as a mobilephone, as an example of the feed unit. However, the feed unit is notlimited to such a home charging tray, and may be applicable to batterychargers of various kinds of electronic devices. In addition, it is notnecessary for the feed unit to be a tray, and may be, for example, astand for an electronic device such as a so-called cradle.

(Example of Feed System Performing Non-contact Electric PowerTransmission Using Electric Field)

Further, the above-described embodiment has been provided by taking, asan example, the case of the non-contact feed system that performs thenon-contact electric power transmission (feeding) using a magneticfield, from the feed unit serving as the primary-side device to theelectronic device serving as the secondary-side device, but this is notlimitative. In other words, contents of the present disclosure areapplicable also to a feed system that performs non-contact electricpower transmission using an electric field (electric field coupling),from a feed unit serving as a primary-side device to an electronicdevice serving as a secondary-side device. In this case, it is possibleto obtain effects similar to those of the above-described embodiment.

Specifically, for example, a feed system illustrated in FIG. 11 mayinclude one feed unit 81 (a primary-side device) and one electronicdevice 82 (a secondary-side device). The feed unit 81 mainly includes apower transmission section 810, an AC signal source 811 (an oscillator),and an earth electrode Eg1. The power transmission section 810 includesa power transmission electrode E1 (a primary-side electrode). Theelectronic device 82 mainly includes a power receiving section 820, arectifier circuit 821, a load 822, and an earth electrode Eg2. The powerreceiving section 820 includes a power receiving electrode E2 (asecondary-side electrode). To be more specific, this feed systemincludes two sets of electrodes, i.e., the power transmission electrodeE1 and the power receiving electrode E2, as well as the earth electrodeEg1 and the earth electrode Eg2. In other words, the feed unit 81 (theprimary-side device) and the electronic device 82 (the secondary-sidedevice) each include, inside thereof, an antenna having a structure ofan asymmetric pair of electrodes such as a monopole antenna.

In the feed system having such a configuration, when the powertransmission electrode E1 and the power receiving electrode E2 face eachother, the above-described non-contact antennas are coupled to eachother (electric field coupling with respect to each other occurs along avertical direction of the electrodes). Then, an induction field isgenerated therebetween, and electric power transmission using theelectric field is performed (see electric power P8 illustrated in FIG.11). Specifically, for example, as schematically illustrated in FIG. 12,the generated electric field (an induction field Ei) may propagate fromthe power transmission electrode E1 side towards the power receivingelectrode E2 side, and the generated induction field Ei may propagatefrom the earth electrode Eg2 side towards the earth electrode Eg1 side.In other words, between the primary-side device and the secondary-sidedevice, a loop path of the generated induction field Ei is formed. Insuch a non-contact electric power supply system using an electric field,by applying a technique similar to that of the above-describedembodiment, it is possible to obtain similar effects.

It is to be noted that the present technology may also have thefollowing configurations.

(1)

A feed unit including:

a power transmission section configured to perform power transmissionusing a magnetic field or an electric field, to a device to be fedincluding a secondary battery; and

a power-transmission control section configured to control powertransmission operation in the power transmission section,

wherein, in a charging period in which charging to the secondary batteryis performed based on transmitted power in the power transmission, whenthe device to be fed including the secondary battery is activated,

the power-transmission control section controls the power transmissionoperation, to increase the transmitted power.

(2)

The feed unit according to (1), wherein the power-transmission controlsection controls the transmitted power, to achieve a power valuenecessary in activation, requested by the device to be fed.

(3)

The feed unit according to (1) or (2), wherein

in a period in which the device to be fed is not activated during thecharging period,

the power-transmission control section reduces the transmitted powerstepwise, to a minimum power value necessary in the charging.

(4)

The feed unit according to (3), wherein, when reducing the transmittedpower stepwise, the power-transmission control section decreases orincreases the transmitted power one step at a time, in response to arequest from the device to be fed.

(5)

The feed unit according to any one of (1) to (4), wherein thepower-transmission control section stops the power transmissionoperation, upon completion of charging to the secondary battery.

(6)

The feed unit according to any one of (1) to (5), wherein thepower-transmission control section detects, by utilizing communicationwith the device to be fed, whether the device to be fed is in thecharging period, and whether the device to be fed is activated.

(7)

A feed system including:

one or a plurality of electronic devices including a secondary battery;and

a feed unit configured to perform power transmission using a magneticfield or an electric field, to the electronic device,

wherein the feed unit includes

a power transmission section configured to perform the powertransmission, and

a power-transmission control section configured to control powertransmission operation in the power transmission section, and

in a charging period in which charging to the secondary battery isperformed based on transmitted power in the power transmission, when theelectronic device including the secondary battery is activated,

the power-transmission control section controls the power transmissionoperation, to increase the transmitted power.

(8)

An electronic device including:

a power receiving section configured to receive transmitted power inpower transmission using a magnetic field or an electric field, from afeed unit;

a secondary battery configured to be charged based on the transmittedpower received by the power receiving section; and

a control section configured to perform predetermined control,

wherein, in a charging period in which charging to the secondary batteryis performed, when the electronic device is activated,

the control section notifies the feed unit side of a request for anincrease of the transmitted power.

(9)

The electronic device according to (8), wherein

in a period before the transmitted power actually increases in responseto the request for the increase of the transmitted power,

the control section performs control to allow activation operation byusing a part of charging power accumulated in the secondary battery.

(10)

The electronic device according to (8) or (9), wherein,

in a period in which the electronic device is not activated during thecharging period,

the control section notifies the feed unit side of a request for astepwise reduction of the transmitted power to a minimum power valuenecessary in the charging.

(11)

The electronic device according to (10), wherein,

the control section notifies a request for a decrease of the transmittedpower by one step, when the transmitted power is larger than the minimumpower value, and

the control section notifies a request for an increase of thetransmitted power by one step, when the transmitted power is smallerthan the minimum power value.

(12)

The electronic device according to (10) or (11), further including:

a charging section configured to perform charging to the secondarybattery; and

a voltage stabilizer configured to perform stabilization of an inputvoltage obtained based on the transmitted power, and to supply thecharging section with an output voltage after the stabilization,

wherein the minimum power value is defined using a magnitude of each ofthe input voltage and the output voltage in the voltage stabilizer.

(13)

The electronic device according to (12), wherein

the voltage stabilizer is configured using a switching regulator, and

the minimum power value corresponds to a magnitude of the input voltage,the magnitude ensuring operation of the switching regulator.

(14)

The electronic device according to any one of (8) to (13), wherein thecontrol section notifies the feed unit side of a request to bring thetransmitted power to a power value necessary in activation.

(15)

The electronic device according to any one of (8) to (14), wherein, uponcompletion of charging to the secondary battery, the control sectionnotifies the feed unit side of the completion.

(16)

The electronic device according to any one of (8) to (15), wherein thecontrol section notifies the feed unit side, by utilizing communicationwith the feed unit.

(17)

A feed system including:

one or a plurality of electronic devices; and

a feed unit configured to perform power transmission using a magneticfield or an electric field, to the electronic device,

wherein the electronic device includes

a power receiving section configured to receive transmitted power in thepower transmission,

a secondary battery configured to be charged based on the transmittedpower received by the power receiving section, and

a control section configured to perform predetermined control, and

when the electronic device is activated, in a charging period in whichcharging to the secondary battery is performed,

the control section notifies the feed unit side of a request for anincrease of the transmitted power.

The present application claims priority based on Japanese PatentApplication No. 2011-279239 filed in the Japan Patent Office on Dec. 21,2011, and Japanese Patent Application No. 2012-94334 filed in the JapanPatent Office on Apr. 18, 2012, the entire contents of each of which ishereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An electronic device, comprising: a power receiving coil configuredto receive wireless power transmitted from a feed device; a voltageconverting circuit configured to generate a predetermined voltage basedon the transmitted power; a battery configured to receive the power fromthe voltage converting circuit; and a control circuit configured totransmit a request to the feed device to: (i) decrease the transmittedpower by one step in response to the transmitted power being larger thana minimum power value, and (ii) increase the transmitted power by onestep in response to the transmitted power being smaller than the minimumpower value.
 2. The electronic device according to claim 1, wherein therequest transmitted by the control circuit indicates to increase thetransmitted power in response to changing from a first state to a secondstate of the electronic device by pushing a button of the electronicdevice, and wherein during the first state, the power receiving coil isconfigured to: receive a first power, which indicates a first powerlevel, in response to storage of a first charge of the battery, receivea second power, which indicates a second power level that is less thanthe first power level, in response to storage of a second charge ofbattery that is greater than the first change, and receive a thirdpower, which indicates a third power level that is less than the secondpower level, in response to a completion of a charging of the battery.3. The electronic device according to claim 2, wherein in response tothe first charge being greater than a predetermined threshold, therequest transmitted by the control circuit indicates to decrease thetransmitted power.
 4. The electronic device according to claim 3, inresponse to the first charge being greater than the predeterminedthreshold, the feed device is configured to stepwise reduce the powerwirelessly transmitted to the power receiving coil from the first powerlevel to the second power level and then to the third power level. 5.The electronic device according to claim 2, wherein the first state hasa first load state and the second state has a second load state which islarger than the first load state.
 6. The electronic device according toclaim 2, wherein the control circuit is configured to control theelectronic device to enter the second state in a period before the powerreceived by the power receiving coil is increased in response to therequest transmitted to the feed device.
 7. The electronic deviceaccording to claim 2, wherein the second state includes a power-on statein which the electronic device is activated in response to a powerbutton of the electronic device being activated, and the first stateincludes a power-off state in which the electronic device is notactivated by the power button.
 8. A feed device, comprising: a powertransmission coil configured to wirelessly supply power to an electronicdevice including a battery; and a control circuit configured to: receivea request transmitted from the electronic device, and determine whetherto control the power transmission coil to increase or decrease the powerwirelessly supplied to the electric device based on the request, whereinin response to receiving the request from the electronic device, thecontrol circuit is configured to: (i) decrease the power wirelesslysupplied to the electric device by one step in response to the powerwirelessly supplied to the electric device being larger than a minimumpower value, and (ii) increase the power wirelessly supplied to theelectric device by one step in response to the power wirelessly suppliedto the electric device being smaller than the minimum power value. 9.The feed device according to claim 8, wherein the control circuitcontrols the power transmission coil to increase the power in responseto changing a first state of the electronic device into a second stateof the electronic device, and during the first state of the electronicdevice, the control circuit controls the power transmission coil to:transmit a first power, which indicates a first power level, in responseto storage of a first charge of the battery, transmit a second power,which indicates a second power level that is less than the first powerlevel, in response to storage of a second charge of battery that isgreater than the first change, and transmit a third power, whichindicates a third power level that is less than the second power level,in response to a completion of a charging of the battery.
 10. The feeddevice according to claim 9, wherein in response to the first chargebeing greater than a predetermined threshold, the request transmitted bythe electronic device indicates to decrease the transmitted power. 11.The feed device according to claim 10, wherein in response to the firstcharge being greater than the predetermined threshold, the controlcircuit is configured to stepwise reduce the power wirelessly suppliedto the electronic device from the first power level to the second powerlevel and then to the third power level.
 12. The feed device accordingto claim 9, wherein the first state has a first load state and thesecond state has a second load state which is larger than the first loadstate.
 13. The feed device according to claim 9, wherein the electronicdevice is configured to enter the second state in a period before thepower received by the power wirelessly supplied to the electronic deviceis increased in response to the request transmitted to the feed device.14. An electronic device, comprising: a power receiving coil configuredto receive wireless power transmitted from a feed device; a voltageconverting circuit configured to generate a predetermined voltage basedon the transmitted power; a battery configured to receive the power fromthe voltage converting circuit; and a control circuit configured totransmit a request to the feed device to: (i) decrease the transmittedpower by one step in response to the transmitted power being larger thanthe minimum power value, and (ii) increase the transmitted power by onestep in response to the transmitted power being smaller than the minimumpower value.
 15. The electronic device according to claim 14, whereinthe request transmitted by the control circuit indicates to increase thetransmitted power in response to changing a first state, in which adisplay of the electronic device is blank during the first state, into asecond state in which information is shown on the display of theelectronic device, and during the first state, the power receiving coilis configured to: receive a first power, which indicates a first powerlevel, in response to storage of a first charge of the battery, receivea second power, which indicates a second power level that is less thanthe first power level, in response to storage of a second charge ofbattery that is greater than the first change, and receive a thirdpower, which indicates a third power level that is less than the secondpower level, in response to a completion of a charging of the battery.16. The electronic device according to claim 15, wherein in response tothe first charge being greater than a predetermined threshold, therequest transmitted by the control circuit indicates to decrease thetransmitted power.
 17. The electronic device according to claim 16, inresponse to the first charge being greater than the predeterminedthreshold, the feed device is configured to stepwise reduce the powerwirelessly transmitted to the power receiving coil from the first powerlevel to the second power level and then to the third power level. 18.The electronic device according to claim 15, wherein the first state hasa first load state and the second state has a second load state which islarger than the first load state.
 19. The electronic device according toclaim 15, wherein the control circuit is configured to control theelectronic device to enter the second state in a period before the powerreceived by the power receiving coil is increased in response to therequest transmitted to the feed device.
 20. The electronic deviceaccording to claim 15, wherein the second state includes a power-onstate in which the electronic device is activated in response to a powerbutton of the electronic device being activated, and the first stateincludes a power-off state in which the electronic device is notactivated by the power button.